function $(id){
        return document.getElementById(id);
    }
function test(){
    var name = $('name').value,
    letterbox = $('letterbox'),
    content = $('content').value;
    if(name!=''&&content!=''){
        letterbox.innerText = name+":"+content+'。';
    }else{
        alert('SB,名字和内容不能为空、凸^-^凸、、');
    }
}